Thermoplastic bag

ABSTRACT

The present invention relates to thermoplastic bag structures which are characterized by having a pair of carrying handles which are formed integrally with the bag walls, and extend upwardly from the open mouth portion of the bag. The configuration of the individual bag handles is such that there is reduced tendency for that portion of the handle which is in the user&#39;s palm, when such bags are loaded are carried, to curl into a small cross sectional area, commonly known as roping. Additionally, the individual bags are constructed so that when the bags are loaded and being carried by the user, the stress points around the bag mouth are distributed to areas which are less likely to rupture and tear as a result of stress concentration.

.Iadd.This reissue application is a continuation application of reissueapplication Ser. No. 07/313,258, filed Feb. 23, 1989, abandoned which isa continuation of reissue application Ser. No. 296,750, filed Aug. 27,1981, abandoned which in turn is a reissue application based upon U.S.Pat. No. 4,165,832, issued Aug. 28, 1979, from application Ser. No.06/922,949, filed Jul. 10, 1978, which in turn is a continuation-in-partapplication of Design application Ser. No. 05/889,319, filed Mar. 23,1978, abandoned. .Iaddend.

1. FIELD OF THE INVENTION

The present invention relates to handled thermoplastic bag structuresand thermally welded individual packs of such bag structures. Thestructure of the bag mouth is especially designed to avoid stressconcentration, while the bag is under load, in areas which aresusceptible to bag splitting and tearing, as a result of such loads.

2. DESCRIPTION OF THE PRIOR ART

In the past bags which were characterized by having carrying handlesthereon were constructed using separate handle elements, distinct fromthe bag structure itself, which were fed for attachment adjacent to theopen mouth portion of the bag. The manufacturing operation to producesuch prior art structures with the separate process set of supplyinghandling element and applying them to the bag was quite cumbersome anduneconomical. More recently however, bag structures have been developed,see for example U.S. Pat. Nos. 4,085,822; 3,352,411 and 3,180,557; thedisclosures of which are incorporated herein by reference, wherein bagsare formed so that the handle carrying elements are formed as anintegral part of the bag structure itself, that is to say the handlesare actually an extension of the bag proper. An example of such a bagstructure is one that is constructed from a flattened tube or aflattened side edge gusseted tube. A flattened portion of such a tube iscut off and sealed along its bottom edge. Conversely, such a bag may beformed by folding a piece of the thermoplastic material on itself, thebottom fold line constituting the bottom part of the bag and heatsealing the upper edge and side wall parts of the bag together. Next a Ushaped cutout is made in the upper portion of the bag to provide anopening or entrance, for the introduction of goods to be packaged. Theopposite edges of the upper portion of the bag structure immediatelyadjacent to the cutout area form loops which may be used to carry suchbag structures when they are loaded. In the case of a gusseted tube suchhandle loops are reinforced, i.e. double ply thickness, by virtue of thepresence of the reentrant or gusset fold in the loop handle members.

Such aforedescribed prior art bag structures present carrying problemsfor the end user, particularly since such structures are made fromextremely thin thermoplastic material i.e., on the order of 0.75 mils orless, there is a tendency of the handle material to roll up and rope inthe hand of the carrier. Additionally such prior art bag structures havea tendency to tear at areas adjacent to the lower portion of the baghandles where carrying stress forces have a tendency to concentrate.

SUMMARY OF THE INVENTION

The bag structures of the present invention eliminates or substantiallyreduce the severity of the structural deficiencies of the prior arthandle bags discussed hereinabove. The present bag structures areprovided with increased amounts of thermoplastic material in the upperhandle areas to substantially reduce the roping tendency of this portionof the handle area when loaded bags are being carried or transported bythe user. Further, the open mouth portion of the present handle bagstructures is particularly designed to eliminate the concentration ofstress forces in those areas of the bag mouth which are especiallysusceptible to splitting and tearing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation view of one form of the bag structures ofthe present invention.

FIG. 2 is a perspective view of the bag illustrated in FIG. 1 in apartially open position.

FIG. 3 is a front elevation view of a modified form of the bag structureillustrated in FIG. 1.

FIG. 4 is a perspective view of an assembled package of bags inaccordance with the present invention.

FIG. 5 is a cross sectional view taken on line 5--5 of FIG. 4.

FIGS. 6 and 6-A are schematic representations of prior art bagstructures.

FIGS. 7 and 7-A are schematic representations of the bag structures ofthe present invention.

FIG. 8 is a graphic representation of the effects of bag handle widthand film gauge on the roping tendency of the upper portions of the baghandles on the bag structures of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

One form of the bag structure of the present invention, shown in FIGS. 1and 2 of the accompanying drawings, generally comprises a bag fabricatedfrom a flattened gusseted thermoplastic tube. Such bags compriseattached upper bag handle members 11 which are sealed along their upperedges at 17. The bag bottom portion is also sealed along the areadesignated as 16. The side edges 15 of the bag structure compriseinwardly folded gussets 14, which allow for bag expansion when the bagsare being loaded and, in the present instance, provides a double plythickness to reinforce and strengthen handle members 11. As shown inFIGS. 1 and 2, the upper portion of the bag structures have been cutaway to form a bag mouth opening. In the bag structures of the presentinvention, it will be noted that the upper portions of handle members 11are wider at their top than at their base in the area adjacent the lowermost portion of the cut away area.

The bag structures of the present invention may be formed intoconvenient unitary bag packs, as shown in FIGS. 4 and 5. Such bag packsare formed by providing a detachable tab member 21 which may beconveniently formed during the cut-out operation employed to form theopen mouth portions of the bag structures. Detachable tab member 21 isattached by a perforated area 23 to the main bag structure 10. Aplurality of such bags may be formed into discrete unitized bag packsby, for example, heat welding and penetration of detachable tabs 21 toform an aperture 22, whereby the bags become joined together by virtueof thermoplastic melting and flowing around the periphery of aperture22. This may be accomplished by utilizing conventional techniques suchas penetrating a plurality of the detachable tabs 21 in areas 22,utilizing a heated blade element which is heated to a temperature tocause penetration of the blade through tabs 21 while fusing theperipheral areas of apertures 22 together. The resultant aperture 22 maybe employed to suspend or support the individual bag packs 20 byextending a support element (not shown) through aperture 22. When it isdesired to remove an individual bag from the pack (shown in FIG. 4),front wall of the uppermost bag is torn free from its tab 21 alongperforated area 23. The rear bag wall may remain attached to tab 21during loading operations. After loading the filled bag may becompletely separated from the pack by tearing away, along perforatedarea 23, the rear bag wall from detachable tab 21. The uppermost bag inthe pack is simply torn away along perforated area 23. Conversely,dependent upon the type of bag loading operation, it may be preferred toinitially remove the front wall of an individual bag from pack 20 bytearing the front wall of the bag along area 23, extending the frontwall to provide a load opening and, after the individual bag has beenloaded, completely removing the bag from bag pack 20 by severing thestill connected rear wall of the individual bag along perforated area23.

In accordance with one aspect of the present invention, removal of theindividual bag 10 or bag pack 20, results in the formation of upwardlyextending tabs 24, as shown in FIGS. 1 and 2, which are positionedadjacent the open mouth portion of the bag, on both the front and rearwalls of the bag. Adjacent each end of tabs 24 are stress relief notches.Iadd.or arcuate areas .Iaddend.12, whose function is described indetail hereinafter.

It will be noted that in the bag structure of the present invention ameans is provided to reduce the roping of the handles in thin gaugethermoplastic handle bags. When the handles of typical prior art handlebags are subjected to heavy bag loads and, when carried, areadditionally subjected to a rolling of the handles across the palm ofthe hand of the carrier, there is a tendency for the film in the handleregion to assume a minimum cross-sectional area, thus, to form a roundcross-section with a small diameter.

This configuration is referred to hereinafter as a "rope". Theundesirable effects of such a roping tendency resides primarily in thefact that the weight of the loaded bag is then supported over therelatively small diameter of the ropes and thus approximates pointloadings across the palm of the hand of the carrier. This ropingtendency increases proportionally as the gauge of the thermoplasticmaterial in the handle portion of the bag is reduced. For obviouseconomic reasons it is preferred to prepare such disposablethermoplastic handle bags with as little resinous material as ispossible, i.e. the thinnest gauge possible consistent with satisfactoryperformance.

In accordance with one aspect of the present invention, means areprovided to add more cross-sectional bulk in the handle region tocompensate for the reduction in bulk attendant to gauge reduction andreduced rope diameter as a result of such gauge reduction. Asparticularly shown in FIGS. 1, 2, and 3 of the accompanying drawings theincrease in bulk in accordance with the present invention isaccomplished by making the upper portions of handle members 11 wider inthe regions where the palm of the hand would typically be placed tocarry the loaded bag. It will be noted that in FIGS. 1 through 3 theinside portions of handle members 11 in the areas generally designatedas 18 and 19 are tapered inwardly towards the side edges 15 of the bagstructures. Such inward tapering provides a means for increasing thewidth of the upper portion of handle elements 11 while maintaining asufficient width of bag opening at the base of handle members 11 topermit ease of loading of products through the open bag mouth.

It will be noted that the difference in structure between the bagillustrated in FIG. 1 and that illustrated in FIG. 3 resides solely inthe design of the taper on the inside of bag handle 11. In the case ofFIG. 3 this taper is uniform and continuous from the top of the handle11 to the base thereof adjacent the radius stress relief notch 12whereas in the case of the handles shown in FIG. 1 the taper is providedby an abrupt radius curvature at point 18 flowing into stress reliefnotch 12.

Accompanying FIG. 8 sets forth in graphic form the effects of varyinggauge on the rope diameter assumed by handle elements 11 when a loadedbag is manually transported. The following formula has been found to bean accurate means of calculating the effect of the rope diameter ongauge variation, the diameter being computed as follows: ##EQU1## with:

D=equivalent diameter of the "rope" (in.)

W=Handle width (in.)

G=gauge (in.)

As shown in accompanying FIG. 8 as the gauge of thermoplastic material,in the present instance low density polyethylene, is reduced the ropediameter decreases. However, as the width of the upper portion of handle11 is increased the pronounced reduction in rope diameter, as the gaugeis reduced, is not as severe whereby the concentrated palm pressureexerted by the handles of a loaded bag is proportionally reduced.

As shown in FIGS. 6 and 6-A, prior art bag structures which have beenassembled into unitized packs and retained in pack form utilizing adetachable tab 21 which was joined to the main bag body by a perforatedarea 23-A, located immediately adjacent the bag mouth, when removed fromsuch a pack were characterized by having nicks or small tears along themouth portion of the bag as a result of having been perforated in thatarea. As particularly illustrated in FIG. 6-A, when such bags wereloaded and subjected to the normal carrying stresses and forcesencountered along the perimeter of the bag mouth, there is a pronouncedtendency for such forces to concentrate at a stress point S. Since, inthis area of the prior art bags, an initial tear in the form of a nickcaused by the perforation operation is already present, such prior artbag structures were particularly prone to rupture and tear.

Conversely, in accordance with the bag structures of the presentinvention, as illustrated in FIGS. 7 and 7-A, by reason of the presenceof a stress relief notch 12 and also by virtue of the fact that theperforated mouth area is restricted to a confined location, i.e.,attached to upwardly extending attached tab 24, when normal stresses,e.g., as a result of being loaded and carried, are applied to the loadedbag structures of the present invention, the stresses tend toconcentrate in area S'. Since in this area S' there are no nicks orslight tears as a result of the perforation operation, there is apronouncedly reduced tendency of the present bag structures to tearduring normal loading and carrying operations.

Although the present invention has been described with preferredembodiments, it is to be understood that modifications and variationsmay be resorted to, without departing from the spirit and scope of thisinvention, as those skilled in the art will readily understand. Suchmodifications and variations are considered to be within the purview andscope of the appended claims.

What is claimed is:
 1. A .[.thermoplastic.]. bag structure comprising afront and rear bag wall and an open mouth top portion, said open mouthportion being characterized by having handles which are located onopposite ends of said open mouth portion, said handles being integralextensions of said front and rear bag walls, said bag being furthercharacterized in that the upper portion of each of said handles issubstantially wider than the lower portion of said bag handles saidlower portions being located adjacent opposite ends of said bag mouth;said bag mouth being further characterized by having stress reliefnotches positioned at opposite ends of said mouth, the upper edges ofsaid mouth extending above said stress relief notches.
 2. A bagstructure in accordance with claim 1 wherein said front and rear wallsare joined together by an integral pleat portion. .Iadd.
 3. A handle bagcomprising a front and rear bag wall and an open mouth top portion, saidopen mouth portion being characterized by having handles which arelocated on opposite ends of said open mouth portion, said handles beingintegral extensions of said front and rear bag wall, said bag beingfurther characterized in that the upper portion of each of said handlesis substantially wider than the lower portion of said bag handles, saidlower portions being located adjacent opposite ends of said bag mouth;said bag mouth being further characterized by having arcuate areaspositioned at opposite ends of said mouth and adjacent the lowerportions of said handles, said handles extending upwardly and inwardlyfrom said arcuate areas, and the upper edges of said mouth extendingabove said arcuate areas and being located closer to the lower portionof said handles than to said upper portion of said handles. .Iaddend..Iadd.4. In a bag structure comprising front and rear bag walls joinedtogether to form a bag bottom, an open mouth top portion opposite tosaid bottom, said top portion characterized by having handles which areintegral extensions of said front and rear walls, said handles havinglower portions located at opposite ends of said open mouth and havingupper portions located farther away from said bottom than is said openmouth; the improvement which comprises, said bag mouth being furthercharacterized by having arcuate areas positioned at opposite ends ofsaid mouth and adjacent the lower portions of said handles, said handlesextending upwardly from one end of said arcuate areas, said bag mouthextending above said arcuate areas and having upper edges which arelocated closer to said lower portions of the handles than to said upperportions of said handles. .Iaddend.